The present invention relates generally to pulse forming generators, and more specifically the invention pertains to a source of high peak-power microwave pulses of short duration for high resolution radar systems. The invention is not limited to the "microwave" region of the spectrum. It will operate at any frequency if built to proper scale.
The generation of short pulses of microwave power at frequencies around GH.sub.z, and above has been accomplished largely by magnetrons, klystrons, and frequency multipliers. Klystrons are generally low power output devices. Magnetrons are highly precise, expensive devices. In both, generally as operating frequencies are increased, the structure size needs to be decreased with reduction in the ability of the device to dissipate heat, thereby placing a practicable limit on both the available power output and on the frequency attainable.
While further extension into shorter wave lengths is possible with frequency multipliers which typically use crystals to distort a generated wave, the power derived from the harmonics falls off very rapidly with increasing frequencies.
The task of generating high peak-power microwave pulses of short duration is alleviated, to some extent, by the systems described in the following U.S. Patents, the disclosures of which are incorporated herein by reference:
U.S. Pat. No. 5,118,969 issued to Ikezi et al; PA1 U.S. Pat. No. 5,006,725 issued to Nawaki et al; PA1 U.S. Pat. No. 5,010,255 issued to Hilal et al; PA1 U.S. Pat. No. 4,894,494 issued to Rosl et al; PA1 U.S. Pat. No. 4,818,892 issued to Oohashi et al; and PA1 U.S. Pat. No. 3,484,619 issued to Proud.
The patent to Nawaki et al discloses a pulse generating unit including a delay unit for delaying an input signal of the pulse generating unit and a comparator unit for comparing an output signal of the delay unit with the above mentioned input signal. The patent to Oohashi et al discloses a laser with a high voltage pulse generator wherein the pulse generator supplies electric energy from a DC power source in an on-off form from a supply voltage to a tank circuit through a transformer, with the switching on and off of the supply voltage being effected in synchronism with the resonance period of the tank circuit. The remaining patents are of similar interest.
Useful amounts of power at wave lengths shorter than 5 mm. have been obtained from spark equipment using resonating dipoles in an insulating fluid. In such devices, a resonant dipole, typically spherical, is spaced between a pair of electrodes. A spark discharge across a gap between the electrode and the resonator excites the natural oscillation of the latter by causing a sudden collapse of the electrical field. The sparks are accompanied by damped trains of waves of random phase. Such devices are, therefore, broad-band radio emitters, and have limited power output. Attempts have been made to increase the number of resonant dipoles by arranging them in long series arrays to increase the power output. While the latter does increase it is not at all in proportion to the added number of dipoles. Also spark gaps have been mounted in microwave cavities, the latter being intended to serve as a resonant filter. Such devices are theoretically high efficiency devices but actually exhibit low power outputs. All of the foregoing devices can be termed harmonic generators in that they are oscillating devices controlled by a resonant element which establishes the fundamental frequency.